1. Technical Field
The present invention relates to a catheter for placement in a blood vessel to supply a medicinal fluid or a nutritional supplement to a patient.
2. Description of Related Art
It is well known to provide a person (hereinafter referred to as a patient) with decreased oral ingestion function, for example due to old age or disease, with a medicinal fluid or a nutritional supplement for a high-calorie infusion through a blood vessel by means of a catheter. It is known to confirm the position of the catheter by incorporating a radiopaque agent (see, for example, JP-U-51 108 389). Such a catheter is formed of a flexible plastic tube and has a section which extends in the axial direction of the plastic tube and which incorporates a radiopaque agent. The radiopaque agent conventionally extends in a circumferential direction around the wall of the plastic tube. Therefore, in a situation where the catheter has been placed in a blood vessel of the patient, the position of the catheter can be confirmed by irradiating X-rays to form an image of the radiopaque agent.
Included among these catheters are double lumen catheters which have two lumens, that is a main lumen and a sublumen, to supply different medicinal fluids through the respective lumens, and also catheters having more than two lumens. However, in such catheters, when the thickness of the section incorporating the radiopaque agent is small, it is difficult to confirm the position of the catheter because the radiographic contrast is reduced. Therefore, in order to improve the radiographic contrast for detecting the radiopaque agent, it is necessary to increase the cross-sectional area (thickness) of the section incorporating the radiopaque agent. However, when the cross-sectional area of the section incorporating the radiopaque agent is increased, there are problems in that the strength of the catheter is reduced, and it is difficult to confirm that the medicinal fluids are passing through the catheter.
Further, it has been proposed for double lumen catheters to incorporate a narrow section incorporating radiopaque agent at two different regions corresponding to the main lumen and the sublumen. However, in this case, it is difficult to distinguish between the main lumen and the sublumen so that the effectiveness is reduced at the time when the catheter is assembled during manufacture. Specifically, during manufacture of the catheter, even though different members, such as adapters, are connected to the main lumen and the sublumen, it is difficult to distinguish between the main lumen and the sublumen and the operation is laborious.
It is an object of the present invention to provide a catheter which improves the effectiveness of contrastradiography and which, at the same time, does not reduce the effectiveness at the time when the catheter is manufactured.